For a Long Term Evolution Advanced (LTE-A) system to support a larger system bandwidth (e.g., 100 MHz) than a Long Term Evolution (LTE) system, there are generally the following two approaches: one way is direct allocation of a frequency spectrum with a bandwidth of 100 MHz as illustrated in FIG. 1, and the other way is aggregation of some frequency spectrum allocated to the existing system into a larger bandwidth for use by a long term evolution multi-carrier system, which is referred to as Carrier Aggregation (CA), where uplink and downlink carriers in the system may be configured asymmetrically, that is, a number of N≧1 carriers may be occupied by a user for downlink transmission while a number of N′≧1 carriers may be occupied for uplink transmission as illustrated in FIG. 2.
As currently defined in the LTE-A system, aggregation of at most 5 carriers can be supported, and a User Equipment (UE) needs to feed back the positive acknowledgement/negative acknowledgment (ACK/NACK) information corresponding to multiple downlink carriers and downlink sub-frames in one uplink sub-frame. As currently defined in the LTE-A system, for a Frequency Division Duplex (FDD) system, the number of ACK/NACK information bits to be fed back by a UE in one uplink sub-frame is determined by the number of downlink carriers configured for the UE and the transmission mode configured for each downlink carrier, that is, the UE needs to feed back ACK/NACK information of N+N0 bits in one uplink sub-frame, where N is the number of downlink carriers configured for the UE, and N0 is the number of downlink carriers with a multi-codeword transmission mode among the N downlink carriers; and for a Time Division Duplex (TDD) system, the number of ACK/NACK information bits to be fed back by a UE in one uplink sub-frame is determined by the number of downlink carriers configured for the UE, the transmission mode configured for each downlink carrier and the number of downlink sub-frames for which the UE needs to feed back ACK/NACK information in the same uplink sub-frame, that is, the UE needs to feed back ACK/NACK information of M×(N+N0) bits in one uplink sub-frame, where N is the number of downlink carriers configured for the UE, N0 is the number of downlink carriers with a multi-codeword transmission mode among the N downlink carriers, and M is the number of downlink sub-frames for which the UE needs to feed back ACK/NACK information in the same uplink sub-frame, and the value of M varies with different uplink and downlink configurations and uplink sub-frames, i.e., M is the number of indexes k in a set of indexes of downlink sub-frames K, {k0, k1, . . . , kM−1}, corresponding to each uplink sub-frame per uplink and downlink configuration in Table 1.
TABLE 1K: {k0, k1, . . . , kM−1}Uplink anddownlinkSub-frame No.configuration01234567890——6—4——6—41——7, 64———7, 64—2——8, 7,————8, 7,——4, 64, 63——7, 6, 116, 55, 4—————4——12, 8,6, 5,——————7, 114, 75——13, 12,———————9, 8,7, 5, 4,11, 66——775——77—
As defined in the LTE-A system, the Physical Uplink Control Channel (PUCCH) format 1b with channel selection and the Physical Uplink Control Channel (PUCCH) format 3 are adopted as multiplexing transmission schemes of ACK/NACK information, where at most 4 bits are transmitted in the transmission scheme of the PUCCH format 1b with channel selection, and at most 20 bits are transmitted in the transmission scheme of the PUCCH format 3. When the UE needs to feed back ACK/NACK information above the foregoing thresholds, the ACK/NACK information has to be bundled so that the number of the ACK/NACK information bits to be fed back does not exceed the foregoing thresholds, and this bundling process can be performed through spatial bundling, time-domain bundling, frequency-domain bundling, etc.
In a Long Term Evolution Release 8/9 (LTE Rel-8/9) system, power control of a PUCCH is performed at the UE side, where the UE calculates the transmit power of the PUCCH based on the PUCCH power control related parameters configured by a base station for the UE and the current scheduling, and for details thereof, reference can be made to 3GPP TS36.213 particularly as follows:
In an uplink sub-frame i, the UE calculates the transmit power PPUCCH of a PUCCH using the following formula 1:PPUCCH(i)=min{PCMAX,P0—PUCCH+PL+h(nCQI,nHARQ)+ΔF—PUCCH(F)+g(i)}[dBm]  Formula 1
Where:
PCMAX is higher layer-configured maximum UE transmit power;
ΔF—PUCCH(F) is higher layer-configured as a power offset value of a different PUCCH format from the PUCCH format 1a, where the PUCCH format in the LTE Rel-8/9 system includes numerous formats which are the PUCCH format 1/1a/1b/2/2a/2b;
h(nCQI,nHARQ) is a power offset value corresponding to the number of bits carried on the PUCCH, where nCQI corresponds to the number of bits of transmitted Channel State Information (CSI) including Channel Quality Indicator (CQI) information, Pre-coding Matrix Indicator (PMI) information, Rank Indication (RI) information and a Precoder Type Indication (PTI) information, and nHARQ corresponds to the number of bits of the transmitted ACK/NACK information;
P0—PUCCH is a target value of PUCCH transmit power which is the sum of two higher layer-configured components, i.e., a cell specific component P0—NOMINAL—PUCCH and a UE specific component P0—UE—PUCCH;
g(i) is an accumulative amount of the power control commands; and
PL is the value of the path loss measured by the UE.
In the LTE Rel-8/9 system, h(nCQI,nHARQ) is defined differently for the different PUCCH formats:
h(nCQI,nHARQ)=0 is defined for the PUCCH formats 1/1a/1b;
      h    ⁡          (                        n          CQI                ,                  n          HARQ                    )        =      {                                        10            ⁢                                          log                10                            ⁡                              (                                                      n                    CQI                                    4                                )                                                                                        if              ⁢                                                          ⁢                              n                CQI                                      ≥            4                                                0                          otherwise                    is defined in a normal Cyclic Prefix (CP) for the PUCCH formats 2/2a/2b; and
      h    ⁡          (                        n          CQI                ,                  n          HARQ                    )        =      {                                        10            ⁢                                          log                10                            ⁡                              (                                                                            n                      CQI                                        +                                          n                      HARQ                                                        4                                )                                                                                                        if                ⁢                                                                  ⁢                                  n                  CQI                                            +                              n                HARQ                                      ≥            4                                                0                          otherwise                    is defined in an extended CP for the PUCCH format 2.
The power control solution of the LTE Rel-8/9 system can be reused as much as possible for the PUCCH power control in the LTE-A system except for the additional transmission schemes in the LTE-A system of the PUCCH format 3, and the PUCCH format 1b with channel selection which is applicable in a scenario with aggregation of multiple carriers, as compared with the LTE Rel-8/9 system, where for the PUCCH format 3, h(nCQI,nHARQ,nSR) is defined as h(nCQI,nHARQ,nSR)=(nHARQ+nSR−1)/3 when the UE is configured with 2 antenna ports for transmission or the UE transmits ACK/NACK and/or SR information of more than 11 bits, and as h(nCQI,nHARQ,nSR)=(nHARQ+nSR−1)/2 otherwise; and for the PUCCH format 1b with channel selection applicable in a scenario with aggregation of multiple carriers, h(nCQI,nHARQ,nSR) is defined as h(nCQI,nHARQ,nSR)=(nHARQ−1)/2. For transmission of ACK/NACK information on a PUCCH, a power offset value corresponding to the number of bits carried on the PUCCH is calculated largely based on nHARQ. As currently defined, nHARQ is determined by the number of Transport Blocks (TBs) actually received by the UE and the number of PDCCH indicating a downlink Semi-Persistent Scheduling (SPS) release actually received by the UE, so as to ensure that the PUCCH transmit power of the UE corresponds to the number of actually scheduled downlink carriers and downlink sub-frames as much as possible to avoid a power waste.
However the foregoing solution suffers from the following technical problems:
When the number of original ACK/NACK information bits to be fed back in an uplink sub-frame determined by the UE based on the configuration exceeds the largest capacity of the PUCCH format 1b with channel selection or the PUCCH format 3, the UE has to bundle the original ACK/NACK information, and at this time it is very likely for the number of the bundled ACK/NACK information bits actually transmitted by the UE is much more possible to be smaller than the number of transport blocks actually received by the UE, and if the UE still calculates the PUCCH transmit power based on the number of actually received transport blocks at this time, the PUCCH transmit power of the UE will be larger than that required for actual transmission, thus resulting in a power waste.